In optical communications systems, an optical link generally comprises an optical transmitter and an optical receiver that are connected to each other by a fiber optic cable comprising one or more optical fibers. The optical transmitter generally includes one or more light sources, such as, for example, one or more light-emitting diodes (LEDs) or laser diodes, which convert an electrical data signal into a modulated light signal. This modulated light signal is then transmitted over an optical fiber cable and is received by the optical receiver. The optical receiver generally includes a light detector, such as, for example, a photosensor, a photodiode, etc., which receives the modulated light propagating in the optical fiber cable and converts the light signal back into an electrical data signal.
The housing of an optical transmitter or receiver includes appropriate electrical circuitry that interfaces with other optical communications equipment. The front face of the housing (which comprises a plastic or similar material) includes a receptacle for receiving a fiber optic connector to which an optical fiber cable is terminated. The optical transmitter and receiver are interconnected by the optical fiber cable.
To secure the fiber optic connector within the receptacle, the receptacle comprises an optical port having features for retaining the connector in the receptacle and for maintaining the end of the optical fiber of the cable in optical alignment with an optics system of the optical transmitter or receiver. The optics system directs light between the ends of the fiber and an active optical element of the optical transmitter or receiver. For example, in a typical optical transmitter, the optics system directs light produced by an active optical element such as an LED or laser diode into the end of the optical fiber retained in the optical port of the receptacle. In a typical optical receiver, the optics system directs light that propagates out of the end of the optical fiber retained within the optical port onto an active optical element such as a photodiode. A popular industrial receptacle known as the Versatile Link receptacle includes a horizontal C-shaped feature defined by opposing elements that protrude from the receptacle.
In Small form factor (SFP) optical communications systems, an optical fiber cable having a transmit optical fiber and an optical fiber cable having a receive optical fiber are terminated on their ends with a duplex connector that plugs into a duplex receptacle of the SFP housing. The duplex receptacle is secured to the housing of the duplex SFP system. The housing of the duplex SFP system is typically configured to be inserted into a cage. The housing includes an optics system, two active optical elements (i.e., a light source and a light detector), and electrical circuitry.
Currently, there are two types of SFP transceivers that are prevalent in the market, namely, systems that use LC connectors and systems that use MTRJ connectors. The most commonly used connector is the LC connector.
In SFP systems that use LC connectors, a duplex LC connector terminates the ends two optical fiber cables, one of which has a transmit fiber and the other of which has a receive fiber. The system housing has a duplex LC receptacle that is configured to receive the duplex LC connector and to lock the connector in the duplex receptacle in optical alignment with the optics system of the SFP system housing.
In some fiber optic applications, glass optical fibers are used whereas in other fiber optic applications polymer optical fibers (POFs) are used. Optical fiber cables that use POFs are more cost effective than optical fiber cables that use glass fibers. POF cables also provides easier field termination than fiber optic cables that use glass fibers, and POFs are less susceptible to dust contamination than glass fibers due to the larger fiber core diameters of POFs. The LC connector and the MTRJ connector are designed to terminate ends of glass fibers, which have small diameters. The LC connector and MTRJ connector are not suited for terminating the ends of POFs because of the large diameter of this type of fiber.